Re: [lttng-dev] 回复： 回复： shm leak in traced application?

[Jonathan Rajotte-Julien via lttng-dev <lttng-dev@lists.lttng.org>]

Hi zhenyu.ren,

Please open a bug on our bug tracker and provide a reproducer against the latest
stable version (2.13.x).

https://bugs.lttng.org/

Please follow the guidelines: https://bugs.lttng.org/#Bug-reporting-guidelines

Cheers

On Fri, Feb 25, 2022 at 12:47:34PM +0800, zhenyu.ren via lttng-dev wrote:
> Hi, lttng-dev team 
>    When lttng-sessiond exits, the ust applications should call lttng_ust_objd_table_owner_cleanup() and clean up all shm resource(unmap and close). Howerver I do find that the ust applications keep opening "all" of the shm fds("/dev/shm/ust-shm-consumer-81132 (deleted)") and do NOT free shm.
>    If we run lttng-sessiond again, ust applications can get a new piece of shm and a new list of shm fds so double shm usages. Then if we kill lttng-sessiond, what the mostlikely happened is ust applications close the new list of shm fds and free new shm resource but keeping old shm still. In other word, we can not free this piece of shm unless we killing ust applications!!!
>   So Is there any possilbe that ust applications failed calling lttng_ust_objd_table_owner_cleanup()? Do you have ever see this problem? Do you have any advice to free the shm without killling ust applications(I tried to dig into kernel shm_open and /dev/shm, but not found any ideas)?
> 
> Thanks in advance
> zhenyu.ren 
> 
> 
> 
> ------------------------------------------------------------------
> 发件人：zhenyu.ren via lttng-dev <lttng-dev@lists.lttng.org>
> 发送时间：2022年2月23日(星期三) 23:09
> 收件人：lttng-dev <lttng-dev@lists.lttng.org>
> 主　题：[lttng-dev] 回复： shm leak in traced application?
> 
> >"I found these items also exist in a traced application which is a long-time running daemon"
>  Even if lttng-sessiond has been killed!!
> 
> Thanks
> zhenyu.ren
> ------------------------------------------------------------------
> 发件人：zhenyu.ren via lttng-dev <lttng-dev@lists.lttng.org>
> 发送时间：2022年2月23日(星期三) 22:44
> 收件人：lttng-dev <lttng-dev@lists.lttng.org>
> 主　题：[lttng-dev] shm leak in traced application?
> 
> Hi, 
>    There are many items such as "/dev/shm/ust-shm-consumer-81132 (deleted)" exist in lttng-sessiond fd spaces. I know it is the result of shm_open() and shm_unlnik() in create_posix_shm(). 
>    However, today, I found these items also exist in a traced application which is a long-time running daemon. The most important thing I found is that there seems no reliable way to release share memory.
>    I tried to kill lttng-sessiond but not always release share memory. Sometimes I need to kill the traced application to free share memory....But it is not a good idea to kill these applications.
>    My questions are: 
>    1. Is there any way to release share memory without killing any traced application?
>    2. Is it normal that many items such as "/dev/shm/ust-shm-consumer-81132 (deleted)" exist in the traced application?
> 
> Thanks
> zhenyu.ren
> 
> 

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-- 
Jonathan Rajotte-Julien
EfficiOS
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